Loin pullers are well known machines used in the meat processing industry for trimming off the backfat of a loin, in particular a pork loin.
As shown in FIG. 1 of the accompanying drawings, the central part or “middle” of the carcass-half of a piece of meat comprises two main parts respectively called “loin” and “belly”. The loin is adjacent to the cut portion of the spinal column. The front portion of the loin contains ribs which are called “back ribs”. The belly which is also called “flank”, is a part which is adjacent to the loin at the opposite of the spinal column. The ends of the ribs which extend along the belly can altogether be separated from the same to form “spare ribs”, or they can be removed individually. After removal of the ribs, the belly is mainly used to prepare bacon. The whole carcass-half is covered by an external layer of fat which extends under the loin and belly. The thickness of this layer of fat depends on several parameters including, inter alia, the size, the origin and the nutrition of the animal. This fat is the one that can be found in bacon. Therefore, it is important from a practical standpoint to keep a proper amount of fat with the belly prior to cutting the same. However, it is important to remove some of the fat extending under the loin to avoid an over load of fat in the final product and have to call for an extra manpower or a complementary equipment to remove this fat if it has not been removed from the loin in the loin puller.
Prior to processing a loin in a loin puller, it is of course necessary to separate it from the belly. So far, there have been two different methods of doing so.
The first method, called “Canadian cut”, consists in completely separating the belly from the loin by completely cutting the carcass-half according to a suitable cutting line which may vary depending on the need. An example of such a cutting line is shown in dotted lines in FIG. 1. Such a cutting can be carried out either manually or by means of another machine located upstream the loin puller or within the same. Once separated, the belly can be directed towards another machine or another working table specially adapted for this purpose, in order to separate the spare ribs. On the other hand, the loin is introduced into the loin puller, in order to trim off its fat.
As a non-limitative example of a loin puller especially adapted to process loins after full separation from the adjacent bellies, reference can be made to U.S. Pat. No. 5,090,939 issued on Feb. 25, 1992 in the name of the Applicant, G.E. LEBLANC INC.
The second method, called “American cut”, consists in cutting (scribing) only the internal part of the carcass-half, that is the upper part of the carcass-half shown in FIG. 1, following the same type of cutting line as above, except for the fat. As a result, the layer of fat remains uncut and maintains altogether the loin and the belly. Then, both of them may be transferred together to a working table where the loin is separated from the belly while leaving some of the loin fat attached to the belly. The main advantage of this method is that it makes it possible to recover part of the fat and meat of the loin together with the belly, which part would otherwise have been left onto the loin and trimmed off by a cutting blade. Usually, this method of processing carcass-halves is carried out manually, even though industrial machines have been proposed to do it.
As a non-limitative example of a loin puller adapted to process loins not fully separated from the adjacent bellies, reference can be made to U.S. Pat. No. 6,336,856 issued on Jan. 8, 2002 also in the name of G.E. LEBLANC INC.
In all the existing loin pullers whatever be their kinds of cut, viz. Canadian or American ones, it is of common practice to use an arcuate cutting blade mounted above the loin conveying system in order to engage the loin while the same is moved forwards, and to cut the layer of fat to be trimmed off from the same, with or without lean meat on the trimmed fat attached to the belly. The arcuate cutting blade is of course “associated” to a control system whose purpose is to adjust the height and curvature of the blade as a function of the size, shape and other characteristics of the loin to be processed, especially the thickness of the layer of fat to be trimmed off. This control system can be operated manually or it can be operated by an automatic measurement system which evaluates the main parameters required for adjusting the cutting blade as a function of the evaluation of the main parameters from trimming off the loin. For further details on this kind of automation, reference can be made by way of non-restrictive examples to the description of the above mentioned U.S. Pat. No. 5,090,939.
In order to maximize yields on bellies as compared to what is achieved when use is made of a conventional arcuate cutting blade, it has already been suggested to use an arcuate cutting blade having a distorted portion (also called “inwardly projecting bend” or “indented bight”) on one of its sides. In this connection, reference can be made to the above mentioned U.S. Pat. No. 6,336,856 to G.E. LEBLANC INC., as well as to U.S. Pat. No. 6,155,919 issued on Dec. 5, 2000 to SWIFT & CO. and U.S. Pat. No. 6,089,968 issued on Jul. 18, 2000 to ACRALOC CORP. Reference can also be made to U.S. Pat. No. 6,547,658 issued on Apr. 15, 2003 to ACRALOC CORP., which discloses a loin puller comprising two blades extending vertically within the conveyor, one of said blades being Z-shaped to fully separate the loin from the belly while leaving lean fingers on the belly to increase the exposed amount of lean meat on the backfat side of the belly, the other one of said blades being J-shaped to trim off the fat and skin from the loin after it has been separated from the belly.
In all above-mentioned cases, the utility and advantage of the distorted portion of the blade is to allow trimming off of the loin close to the ribs while leaving lean fingers of meat on the belly.
It is worth noting however that there is a basic difference between the way the arcuate cutting blade with a distorted portion disclosed in G. E. LEBLANC's U.S. Pat. No. 6,336,856 is used and the way the blade disclosed in the three other patents mentioned hereinabove, is used. In G. E. LEBLANC's U.S. Pat. No. 6,336,856, the arcuate cutting blade is exclusively used to trim off the fat and skin (also called “backfat”) from the back of the loin while simultaneously leaving fingers of meat on the belly. The arcuate cutting blade separates the loin from the central part of the carcass half but it does not separate the fat and skin trimmed off from the loin from the adjacent belly. In full contrast, in SWIFT & CO's U.S. Pat. No. 6,155,919 and ACRALOC CORP.'s U.S. Pat. Nos. 6,089,968 and 6,547,658, the arcuate cutting blade(s) is (are) used to fully separate not only the loin itself but also its fat and skin from the belly while leaving fingers of meat on the same. In U.S. Pat. Nos. 6,155,919 and 6,089,968, a single cutter blade is used just to separate the loin from the belly while leaving the skin and fat intact on the back of the loin (see and compare FIGS. 2 and 3 of U.S. Pat. No. 6,155,919 and FIGS. 18 and 19 of U.S. Pat. No. 6,089,968 and the corresponding parts of their specification). In U.S. Pat. No. 6,547,658, another blade is used to trim off the fat and skin from the loin. However, even if the fat and skin are trimmed off from the loin, the fat and skin are also separated from the belly either at the same time or just before.
If arcuate cutting blades with a distorted portion are interesting for the above mentioned reason, they have the drawback of being very difficult to make in one piece with an appropriate and efficient sharpened edge. Thus, in practice, the requested cutting especially close to the ribs without risk of hitting them and also hitting the blade bone, is quite difficult to be achieved with good results, especially in the case where, like in G. E. LEBLANC's loin puller, the arcuate part of the cutting blade is mainly used to separate the loin from the belly while trimming off the fat and skin from the loin and leaving them attached to the adjacent belly.